A massive multiple input multiple output (MIMO) technology is one of key technologies of a 5th generation (5G) communications system, as universally acknowledged. In the massive MIMO, large-scale antennas are used, so that spectrum efficiency is remarkably improved. Accuracy of channel state information (CSI) obtained by a network device determines performance of the massive MIMO to a great extent. In a frequency division duplex (FDD) system or a time division duplex (TDD) system in which channel reciprocity cannot be better satisfied, a codebook is usually used, to quantize CSI information. Therefore, codebook design is a key issue of the massive MIMO.
In the prior art, one optimal codeword is selected from a plurality of candidate codewords, and the selected codeword is reported as CSI information in a form of a precoding matrix indication (PMI). Massive MIMO using a new radio (NR) technology imposes a higher requirement on channel state information feedback. The foregoing mechanism cannot satisfy a high-precision CSI requirement of the NR. In view of this, currently, in the NR, a discussion of high-precision CSI feedback mechanism design mainly focuses on a method for representing CSI by linearly superposing a plurality of codewords, so that a quantization precision loss caused when CSI is represented by using a single codeword is compensated for, and CSI feedback quality is remarkably improved.
For the method for representing CSI by linearly superposing a plurality of codewords, an information feedback method needs to be provided, to improve channel state information feedback precision.